This invention relates to a lighting unit with a reflecting mirror used for lighting up goods at stores or the like, i.e., a lighting unit having a bulb with a reflecting mirror.
A conventional lighting unit with a dichroic reflecting mirror is disclosed in U.S. Pat. No. 5,272,408. The lighting unit is produced by combining a funnel-shaped reflecting mirror which has a reflecting mirror surface provided with a dichroic film, as a light interference film and a bulb, such as a tungsten halogen lamp. Such lighting units with dichroic reflecting mirrors are used for lighting goods at stores or the like. As shown in FIG. 4, such a lighting unit with a reflecting mirror includes a funnel-shaped reflecting mirror 23 having a reflecting part 25 and a neck portion 26, and, as a light source, a bulb, such as a straight tungsten halogen lamp 21, provided inside the reflecting mirror 23. A tungsten filament 30 is provided within the tungsten halogen lamp 23. The reflecting part 25 has a reflecting surface provided with a dichroic film 24, while the neck portion 26 is connected with the reflecting part 23. The tungsten halogen lamp 21 is inserted and sealed into a base 28 at the upper position.
The tungsten halogen lamp 21 is substantially coaxially located inside the reflecting mirror 23. The neck portion 26 of the reflecting mirror 23 and the sealing portion 22 of the tungsten halogen lamp 21 are inserted into the base 28 and combined into one component by injecting an inorganic adhesive 29 into the base 28.
In the conventional lighting unit with a reflecting mirror, it is desired that as much of the light and dark image of the coiled tungsten filament 30 contained in the tungsten halogen lamp 21 as possible is prevented from being seen on the irradiated surface during lighting, so that the illuminance of the irradiated surface will be uniform and any irradiation nonuniformity on the irradiated surface can be avoided. For this purpose, fine reflecting surfaces 25a (FIG. 5) are formed on the reflecting surface of the reflecting part 25 in order to scatter the reflected light appropriately. More specifically, hexagonal fine reflecting surfaces 25a are radially arrayed in good order without leaving clearance, and the fine reflecting surfaces become smaller gradually from the opening part 27 of the reflecting mirror 23 toward the neck portion 26.
In the conventional tungsten halogen lamp with a reflecting mirror, hexagonal fine reflecting surfaces 25a are formed without clearance. As a result, concave or convex boundary lines 25b are formed at the borders of adjacent fine reflecting surfaces 25a in radial lines from the opening part 27 of the reflecting mirror 23 to the neck portion 26. Light that falls on the boundary will not be scattered, and thus, irradiation nonuniformity, such as radial lines, occurs on the irradiated surface.
As shown in FIG. 6, the luminous intensity distribution of the conventional tungsten halogen lamp with a reflecting mirror has irregularities in the curve before the light intensity comes to the peak. The irregularities indicate the radial linear difference between the bright parts and dark parts, which causes nonuniformity in irradiation.
In order to solve the problems of the conventional units, this invention aims to provide a lighting unit with a reflecting mirror that can prevent irradiation nonuniformity on the irradiated surface.
To achieve the aims, a lighting unit with a reflecting mirror of this invention includes a bulb as a light source, arranged inside a funnel-shaped reflecting mirror having a reflecting surface, and a plurality of fine reflecting planes that are arranged on the reflecting surface non-centrally originating and non-radially without clearance.
It is preferable in the lighting unit with a reflecting mirror that the shapes of the fine reflecting surfaces are at least one shape selected from the group consisting of a circle, an ellipse, and a polygon.
It is preferable in the lighting unit with a reflecting mirror that the fine reflecting surfaces are concave or convex.
It is also preferable in the lighting unit with a reflecting mirror that the surface of each fine reflecting surface is dented or protruded in the range of 0.01 to 1.0 mm.
It is also preferable in the lighting unit with a reflecting mirror that a dichroic film is provided on at least one wall surface of the reflecting mirror. Here, a dichroic film refers to a light interference film formed by alternately laminating a high-refractive layer including zinc sulphide (ZnS) and a low-refractive layer including magnesium fluoride. The film radiates a visible light emitted from the light source on the front surface of the mirror, and selectively lets an infrared ray go to the back of the mirror.
It is also preferable in the lighting unit with a reflecting mirror that the size of the fine reflecting surfaces on the entire reflecting surface is not varied substantially. The term xe2x80x98not varied substantiallyxe2x80x99 means that slight differences due to manufacturing processes is permissible.
It is also preferable in the lighting unit with a reflecting mirror that the luminous intensity curve is smooth when the beam angle just beneath the light source is 0xc2x0 and the beam angle at the neck portion of the same light source is 90xc2x0. When the curve of the luminous intensity distribution is smooth before it comes to a peak and has no irregularities, the brightness is not varied in radial lines and there is no irradiation nonuniformity.
It is also preferable in the lighting unit with a reflecting mirror that the appearance of the fine reflecting surfaces is a honeycomb, so that the fine reflecting surfaces can be formed without clearance.
It is also preferable in the lighting unit with a reflecting mirror that the size of the fine reflecting surfaces ranges from 0.01 to 5 mm long, and from 0.01 to 5 mm wide.
It is also preferable in the lighting unit with a reflecting mirror that the bulb as a light source is at least one selected from the group consisting of a tungsten halogen lamp and a discharge lamp.